[R-SIG-Mac] flushing of stdout

[Simon Urbanek]

On Aug 23, 2007, at 4:24 AM, Joerg van den Hoff wrote:

> On Wed, Aug 22, 2007 at 02:52:55PM -0400, Simon Urbanek wrote:
>> Joerg,
>>
>> On Aug 22, 2007, at 11:20 AM, Joerg van den Hoff wrote:
>>
>>> I post this here, since maybe it's only a Mac problem.
>>>
>>>
>>> I noted only now an apparent change of behaviour in 2.5.0 relative
>>> to older times:
>>>
>>
>> I'm not aware of any such change. For me the output is still shown
>> progressively, e.g.:
>>
>> for (i in 1:10) { cat("foo",i,"\n"); rnorm(1e7); }
>>
>> Can you, please, send us a reproducible example?
>>
>>
>>> I use `cat' to stdout from within a long running loop to report
>>> the loop count to the user. this output is now delayed until the
>>> program
>>> completes (i.e. the output is buffered) and, thus, does not make
>>> much sense
>>> anymore...
>>>
>>> issuing `flush(stdout())' after the `cat' does not help.
>>>
>>
>> .. and it's not meant to (since the R console has nothing to do with
>> stdout) - try flush.console() instead ...
>>
> yeah,  sorry for being inprecise: I'm actually using R frequently
> in a terminal/xterm.
>
> in the R GUI console flush.console() (as also proposed by kevin
> middleton: many thanks) actually achieves the desired flushing  
> (without
> it: same thing)
>
> so the problem persists in the terminal/xterm. try, e.g.,
>

Ah, that's a different story. You can avoid that by setting TERM=dumb  
(what ESS uses).
The change is actually much older (pre-2.5). In theory flush.console  
should help here, but apparently it doesn't - I'll see if I can fix  
that.

Cheers,
Simon


>
> for (i in 1:10) {
>    for (j in 1:20000) log(j)
>    cat(i, " ")
>    flush(stdout())
> }
> cat("\n")
>
>
> to see the effect. this only occurs if the first `cat' does not  
> contain a
> newline (I use this in situations with a large outer loop count to  
> inform the
> user how much the simulation run has progressed and it's simply  
> nicer without
> too many newlines).
>
> the behaviour was definitely different in older versions of R.
>
>
> regards,
>
> joerg
>
>